ASoC: rsnd: enable clock-frequency for both 44.1kHz/48kHz

Current clock-frequency allows only 1 clock, but ADG can
handle both 44.1kHz/48kHz base clocks. This patch enables these.

On Salvator-X board, AUDIO_CLKOUT which is generated by ADG
is connected to ak4613 MCKI, and it should be synchronized with
LRCK. Thus, we need both 44.1kHz/48kHz base clock-frequency.
Otherwise, either one sounds strange in high frequency sound.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Tested-by: Hiroyuki Yokoyama <hiroyuki.yokoyama.vx@renesas.com>
Signed-off-by: Mark Brown <broonie@kernel.org>